U.S. Pat. No. 5,247,571 to Kay et al. discloses an area-wide Centrex service. Among the features provided by the area-wide Centrex service is an extension dialing feature. The extension dialing feature allows a multi-location customer to provide a specialized, abbreviated dialing plan for calls between multiple locations. Using this feature, an area-wide Centrex station user can call any other station in the area-wide Centrex network using the specialized dialing plan. This feature offers multi-location Centrex customers a uniform abbreviated dialing plan between their PBX locations, Centrex locations, ISDN lines, and residential lines for people working from home.